Modern oscilloscopes have the ability to detect anomalies in waveforms using a boundary mask. The boundary mask defines an area within which the waveform is expected to reside. This anomaly detection is accomplished on a pixel by pixel basis. If pixels can be identified as violation pixels in a display pixel plane (a boundary mask), when a digitized signals is presented in two dimensions, it can be determined whether the shape is or is not valid. When the waveform crosses the boundary of the mask, an anomaly can be detected, and any desired course of action can be taken: the oscilloscope can pause waveform acquisition, can alert the user, or can take other action, as desired.
But current oscilloscopes only use one boundary mask relative to all waveform acquisitions: the boundary mask has a static shape. That is, the boundary mask represents the limits of all possible waveform acquisitions. While using a single static boundary mask ensures that any violations detected by the oscilloscope are true anomalies, a single static boundary mask also means that some anomalies in the waveform might not be detected using the static boundary mask.
Consider, for example, the waveform acquisitions shown in FIG. 1, which shows two acquisitions of a waveform over time. In acquisition 105, the waveform is generally uniform, except for a peak at frequency 110. In acquisition 115, the waveform is generally uniform, except for a peak at frequency 120. Boundary mask 125 represents a single static boundary mask that determines where anomalies might occur over the entire acquisition of the waveform, and can be applied to both acquisitions 105 and 115.
But if acquisition 105 were to have a peak at frequency 120, this would be an anomaly: a departure from the expected form of the wave at the time of acquisition. Similarly, a peak at frequency 110 in acquisition 115 would be an anomaly. But in each case, because these anomalous peaks might not cross the edge of boundary mask 125, the oscilloscope would not detect the anomaly and take any appropriate action.